1. Field of the Invention
The present invention relates to a recording apparatus for recording data by using a head scheduling process.
2. Description of Related Art
Storage of a large capacity such as HDD and optical discs are used nowadays as devices for recording moving images and audio data in consumer AV equipment. A PC, which accesses a large capacity storage and executes processes such as data recording, is required to increase the number of processed commands or data traffic per unit time. However, much attention has not paid to a variation in these number and amount. The data traffic is calculated as an average value in a relatively long time.
Performance (specifications) including data traffic of consumer AV equipment such as digital cameras and video cameras is not required to be much higher than that of HDD. For example, a data rate of consumer equipment is about 25 Mbit/sec even if standard MPEG2 is used for recording High Definition (HD) data, and this data rate is not so high from the viewpoint of an HDD transfer rate exceeding 10 Mbit/sec.
However, a small diameter HDD is adopted recently as recording media of compact portable consumer AV equipment such as video cameras and digital cameras. Generally, this small diameter HDD has a lower data transfer rate than those of HDD having a disk diameter of 3.5 inches and HDD having a disk diameter of 2.5 inches, and can not meet sufficiently the requirements of high image quality recording. Further, in HDD, since the transfer rate drops (is lowered) generally in a disk inner circumferential area more than in a disk outer circumferential area. For example, problems may occur in some cases, such as stoppage of images and audio data during playing back data and inability of recording images during data recording. These problems are serious about using consumer AV equipment employing HDD as a storage. Furthermore, the transfer rate of consumer AV equipment is lower further because of a retry process and the like to be executed due to a seek error of a head mounted on HDD or an error in read data.
The first problem of a lowered data transfer rate can be avoided by setting consumer AV equipment to neglect errors of AV data and the like allowed to have low data reliability, by setting an upper limit of a command process time, or the like. For example, in Streaming Feature Set, AV command of ATA-7, a process time of each command can be designated directly.
However, how a designated command is executed relies completely upon a storage, typically HDD, so that it cannot guarantee whether data is correctly written/read in/from the disk. An occurrence frequency of the problem of this type is very low in practical usage.
The second problem such as a seek error has a higher occurrence frequency than that of the first problem and is more serious. As a solution method for this problem, a process of devising a physical layout of files has been proposed, and many researches have been conducted.
For example, in a proposed file system, a device of disposing related data at physically nearby positions is realized in a logical block address (LBA) space by utilizing data locality. As a file physical layout method, a method (hereinafter called a head scheduling process) has been proposed, as in FIG. 13, by which a low transfer rate area and a high transfer rate area are used in combination although a seek operation is performed frequently in order to guarantee a minimum seek time.
The recent spread of PCs and digital cameras makes it general to edit images taken with imaging apparatus. If a magnetic tape is used as media for storing photographed data, it takes very long time to read data from the magnetic tape, to transfer the read data to PC and to search desired images. This problem results in an inferior quick response. It is thus desired to use HDD as media of imaging apparatus, because HDD has an excellent quick response and fair advantages in terms of data transfer rate and random access.
Data recorded in HDD is managed by using a file system such as a FAT, and it becomes necessary to record file management information including directory information, FAT information to be used for data reading in addition to a write operation of photographed data itself. For example, in a case of a FAT file system as a general file system, file management information is recorded in a predetermined area of HDD before a recording operation for photographed data and after the recording operation. If file management information is not written, data reading is impossible.
Imaging apparatus such as a video camera is a system for recording long-time photographed data. If HDD is used with the apparatus of this type and a power shutdown of the apparatus occurs, for example, by dropping the apparatus during photographing (recording) an object, the file management information cannot be written, so that all data photographed up to that time is lost.
Namely, if the file management information is not recorded because of the power shutdown, the photographed data cannot be distinguished as a file, and the recorded image file without the file management information cannot be read. In a case where a magnetic tape is used for recording, even if power shutdown of a video camera occurs during photographing, data immediately before the power shutdown can be retained.
In order to solve the above-described problems, a method has been proposed by which file management information is updated each time data is recorded. For example, refer to Japanese Patent Application Publication (KOKAI) No. 2003-30925.